Refrigerating apparatus



26, 1941; F. w. JORDAN REFRIGERATING APPARATUS Filed May 18, 1937INVENTOR FRANK W. Jonnn'u ATTORNEZ I WITNESSES:

. r l I I Patented Aug. 26, 1941 REFRIGERATIN G APPARATUS Frank W.Jordan, San Francisco, Calif., assignor to Westinghouse Electric &Manufacturing Company, East Pittsburgh, Pa., a corporation ofPennsylvania Application May 18, 1937, Serial No. 143,215 3 Claims.'(Cl. 230-206) receives more than its share of oil, the oil level Myinvention relates to refrigerating apparatus comprising a plurality ofcompressors, more particularly a plurality of compressors connected inparallel to a common suction line, and it has for an object to provideimproved means for eflecting-proper distribution of lubricating oil tothe several compressors.

In the operation of a refrigerating system, the refrigerant passingthrough the compressor .entrains some of the oil used for lubricatingthe compressor. The refrigerating system is arranged, so that this oilis carried by the refrigerant completely through the refrigeratingsystem and returned to the compressor by the suction gas. Such return ofoil is depended upon to maintain the proper supply of oil in eachcompressor. When a plurality of compressors are connected in parallel ina refrigerating system,

as where there is a common suction line,the oil is not returned to theseveral compressors in the proper proportions. It is necessary,therefore, to provide some arrangement for equalizing or distributingthe quantity, of 011 among the several compressors.

Heretofore, such equalization has been effected by an equalizing passageconnected to the bottom of the crankcase of each compressor, the objectbeing that the oil level in the crankcase of the compressor receivingmore than its share of oil will rise and cause gravity flow of oil tothe other crankcases until a common level and .proper distribution ofoil is obtained. It has I been found, however, that the pressures of theseveral crankcases arenot always equal; the

pressure in the crankcase of a compressor that is in operation beinglower than the pressure of a crankcase that is idle. The higher pressurein the'idle compressor caused flow of oil through the connecting passageto the operating compressor to such an,,gextent as to substantiallyempty the crankcase of the idle compressor.

When the idle compressor was started, there was found to be insumcientoil for proper lubrication thereof. 1 g

It is an object of my invention, therefore,to arrange the oil equalizingpassage in such a way that onlythe quantity of oil in excess of thenormal quantity in one compressor may flow through the equalizingpassage to another compressor, so that sliflicient oil is retained ineach a compressor for operation thereof.

In accordance with my invention, I connect the w oil equalizing passageto the crankcase or oil sump of each compressor at substantially thenormal oil level therein. When one compressor rises above the normallevel so that the oil may flow through the equalizing passage to anothercompressor. The normal quantity of oil for the compressor is disposedbelow the connection with I the equalizing passage so that it cannotflow I the reciprocating type.

therethrough, and thus a suflicient quantity of oil is retained in eachcompressor for operation thereof notwithstanding unequal pressuredifferences tending to cause flow into another compressor.

I prefer also to provide a second pressure equalizing passage connectedto the crankcases or oil sumps of the several compressors above the oillevel therein, so as to facilitate pressure equalization and gravityflow of oil for equalization.

The above and-other objects are effected by my invention as will beapparent from the following description and claims taken in connection.with the accompanying drawing forming a part of this application, inwhich:

The single figure is a diagrammatic view of apparatus embodying myinvention.

Referring to the drawing in detail, I show three compressors, I I, I2and it connected to a common refrigerating system and disposed at thesame level. The discharge outlets H of the several compressors areconnected through branch conduits l5 to a common discharge line 16, andthe suction inlets ll of the several compressors are connected throughbranch conduits IE to a common suction line l9. The discharge line I 6is connected to a condenser 2| which in turn is connected to a liquidreceiver 22. A liquid line 23 connects the liquid receiver with torsforms no part of the present invention, it

is not further described herein. The several evaporators'are connectedat their outlet ends to the common suction line 19.

The compressors shown on the drawing are of Each includes a crankcase3|, which provides an oil sump or reservoir for thecompressor. Eachcompressor also includes a motor 32 which, in the present embodiment hasa casing common with the compressor thereby providing a hermeticallysealed motor compressor unit.

Each crankcase is maintained at suction pressure by means of a passage33 communicating between the crankcase and the suction inlet IT. Thispassage also permits oil returned by the suction line through the inletl1 to drain by gravity into the crankcase. Such arrangements are wellknown in the art.

The bottom of the crankcase serves as a reservoir or sump for oil forlubricating the compressor. The normal liquid level is indicated at 34.The compressor is lubricated in any suitable manner, as by an oil pump,by oil from the crankcase. Inasmuch as the particular form oflubrication-system is not a part of the present invention, it is notfurther described herein. An oil equalizing conduit 35 is connected,through branch conduits 35 to the several crankcases at substantiallythe normal liquid level therein. The connection is preferably disposedso that the bottom of the opening into the crankcase is at the normalliquid level. A shut-off valve 31 may be provided in each branch conduit36 to permit isolation of the compressor. The oil equalizing conduit 35and the branch conduits 35 may extend downwardly as shown on thedrawing, but, in order to assure gravity flow of oil therethrough,should not at any point extend above the conneotons with the severalcrankcases. I prefer, also, to provide a pressure equalizing conduit 38connected through branch conduits 35 to the several crankcases at alevel sufficiently high to be above the oil level in the severalcrankcases at all times. The branch conduits 39 may also be providedwith shut-ofl valves 40.

If desired, a suitable form of control mechanism may be provided forautomatically controlling the operation of the several compressors. Forexample, a bellows 4| may be connected through a tube 42 to the suctionline I9. The bellows 4| is arranged to close switches 43, 44, and 45successively upon successive increases in suction pressure and viceversa. The switches 43 to 45 control circuits 46, 41, and 48, whichsupply current to the motors of the compressors II, I! and I3,respectively.

Operation The refrigerating system operates in the usual manner of suchapparatus. Refrigerant is compressed by any compressor in operation anddischarged under high pressure through the branch conduit l5 into thedischarge line l5. It is condensed in the condenser 2| and collected inthe liquid receiver 22. The liquid refrigerant is conveyed through theliquid line 23 to the evaporators whose valves 21 are open. The flow ofrefrigerant to each evaporator is regulated by the expansion valve 28 aswell understood in the art. The refrigerant is evaporated in theevaporator and then returned through the suction line iii to suchcompressor or compressors as are in operation.

The bellows 4| controls the several compressors in response to thesuction pressure in the suction line l9. Upon successive increases insuction pressure, the switches 43, 44, and 45 are.

successively closed and, upon successive decreases in pressure,the-switches are successively opened in the reverse order, all as willbe apparent and readily understood by one skilled in the art.

The compressed refrigerant discharged from any compressor in operationcarries a certain amount of entrained lubricating oil-therewith.

ing system and returned through the suction line l9. It will be apparentthat the suction line l9 will not necessarily return the oil to theseveral compressors by the same amounts that oil is removed therefrom.Therefore, an oil equalizing passage, such as the conduit 35, isprovided. When all the compressors are idle, the pressures in theseveral crankcases may readily equalize, this being facilitated by thepressure equalizing conduit 33. If one crankcase has a surplus quantityof oil, raising its oil level above the normal, the excess quantity mayflow through the equalizing conduit 35 to the other crankcase orcrankcases, so as to provide substantially normal oil level in eachcrankcase and to provide sumcient oil for operation of each municationwith the crankcase of the compressor. ll through the suction line I3 andthe pressure equalizing passage 38,, nevertheless, it is found that thepressures in the crankcases of the idle compressors l2 and iii areappreciably higher than the pressure in the crankcase of the operatingcompressor H, due to the pressure drop through the connecting conduits.Where the oil equalizing conduits have been connected to the bottom ofeach crankcase. such pressure difference has resulted in forcingsubstantially allof the oil from the crankcase of ,an idle compressor tothe crankcase of a compressor in operation. This possibility is avoidedby the present invention by connecting the oil equalizing conduit 35substantially at the normal liquid level. Therefore, only the quantityof oil in the crankcase in excess of the normal quantity therein canflow through the equalizing passage to another crankcase. The normalquantity of oil in the crankcase is below the connection and thereforewill not flow through the connection to the oil equalizing passage,regardless of pressure conditions in the several crankcases.

While I have shown my invention in connectionv with a refrigeratingsystem comprising a common condenser and several evaporators exhaustinginto a common suction line, it is to be understood that such system isto be taken as exemplary and not as limiting. The invention isapplicable to a wide variety of systems having refrigerant-containingmeans common to several compressors, so that the oil from the severalcompressors is intermingled and proper distribution 3 the severalcompressors is necessary. It is ore particularly applicable torefrigerating systems in which there is common refrigerant-containingmeans in the low pressure side of the system and wherein the compressorsoperate at substantially the same evaporator or suction pressure.

While I have shown my invention in but one erant compressors connectedto a common refrigerant-containing means and each having an oil sump,one 01 said compressors being adapted to be operated while another isidle, of conduit means providing a passage, open at all times that anycompressor is in operation, for flow of oil from one sump to another,said conduit means being connected to each sump at a level such thatsumcient oil remains in the sump below the connection for operation ofthe compressor.

' 2. In refrigerating apparatus, the combination of a plurality of-refrigerant compressors connected to a common refrigerant containingmeans and having oil sumps disposed at a common level, one of saidcompressors being adapted to be onerated while another is idle, and anoil equalizing art passage connected to each oil sump at substantiallythe normal liquid level therein, whereby flow of oil from one 011 sumpto another to the extent of depriving said one oil sump of a sumcientsupply of oil is avoided, said passage being open and permitting flow ofoil therethrough at all times that any compressor is in operation.

3. The combination with a plurality of refrigerant compressors connectedto a common refrigerant-containing means ande'ach having an oil sump,one of said compressors being adapted I to be operated while another isidle, of an .oil

equalizing passage connected to each oil sump at such a level that thereis sufllcient oil in the sump below the connection for operation of thecompressor, and means providing communication between the several oil'sumps abovethe normal liquid level to provide pressure equalization.

